Measurements of uterine volume: a comparison between measurements by ultrasonography and by water displacement

The uterine volume was measured in 30 patients 24 hours before hysterectomy by ultrasonography using the prolate ellipsoid formula. At hysterectomy the volumes of the same uteri were measured again by water displacement. A comparison is made between the two methods of measurements. Although the correlation between the methods is high (r = 0.964) and the mean percentage bias very small (+2.0%), the agreement between the methods for 95% of subjects is between -33.6, 8% and +37.6%. This is a potentially large disagreement relative to the typical size of the uterus, indicating that ultrasonic uterine volume measurement by the prolate ellipsoid method is not adequately precise for clinical management of the individual patient.